In the lithographic printing process, a lithographic plate comprising an aluminum sheet is initially coated with a photosensitive layer. A negative is applied over the photosensitive layer and the two are exposed to high intensity light, the negative is then removed, and the plate is processed to develop it. Although some manual developing is still done, the large scale commercial use of lithographic plates has made automatic processing of necessity. Numerous apparatus have been proposed to perform such processes. In general, the more successful machines have emulated the normal development procedures by subjecting the plate to a scrubbing action while flooding the plate with developer liquid and then flooding the plate with gum arabic. However, there has always been need to improve the apparatus to perform tasks more satisfactorily.